by Greg Mayer
To give a little equal time to other trophic levels, this Saturday we have a meadow vole, a member of the rodent family Cricetidae.
Nicknamed ‘Voley’, this Microtus pennsylvanicus was rescued from a mechanical access shaft into which it had fallen and become trapped. What many people think of as ‘field mice’, and what many house cats bring home, are actually voles: they can be distinguished by their short tails, and smaller eyes and ears compared to other mice. Evolutionarily, meadow voles are known for being geographically variable, with many described subspecies, including a number restricted to small islands off the coast. Since most of these islands are land-bridge islands, isolated from the mainland only since the post-glacial rise in sea level, the differentiation of the voles inhabiting them is quite recent. The most distinctive of these small island derivatives of the meadow vole is a distinct species, the beach vole, Microtus breweri, found only on Muskeget, a very small island to the west of Nantucket Island, Massachusetts. (My friend and colleague James ‘Skip’ Lazell calls it “defiantly” distinct from the meadow voles on nearby islands.) They have been isolated on Muskeget only 2000-3000 years, and are thus an example of rapid divergence. Jerry deals with the nature of species and species formation in chap. 7 of WEIT, and in much more detail in his 2004 monograph with H. Allen Orr, Speciation.
I’ve never been to Muskeget island but have seen it from Chappaquiddick island of Martha’s Vineyard.
Thanks for the heads up that most ‘field mice’ are actually voles.
With a diet of grasses, bark, nuts, seeds, etc. It will not likely become extinct.
Very interesting. Good work.
Hey, I know Skip! Great guy.
The non-vole cricetids that I think of as the ‘true’ field mice are the mice of the genus Peromyscus. Two species that are common in the eastern US and Canada are the white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus). A lot of really interesting evolutionary work has been done on mice of this genus. Jerry discusses some of this work in WEIT. GCM